Closing in on singlet scalar dark matter: LUX, invisible Higgs decays and gamma-ray lines

TL;DR

This paper analyzes how recent dark matter and Higgs data constrain singlet scalar dark matter models, highlighting the importance of direct and indirect detection methods in narrowing down viable parameter space.

Contribution

It provides a comprehensive analysis of the parameter space of singlet scalar dark matter considering latest experimental constraints, emphasizing the role of gamma-ray line searches.

Findings

LUX results significantly restrict the model's parameter space.

Higgs invisible decay constraints affect low-mass dark matter.

Gamma-ray line searches limit viable masses near half the Higgs mass.

Abstract

We study the implications of the Higgs discovery and of recent results from dark matter searches on real singlet scalar dark matter. The phenomenology of the model is defined by only two parameters, the singlet scalar mass $m_S$ and the quartic coupling $a_2$ between the SU(2) Higgs and the singlet scalar. We concentrate on the window $5 < m_S/{\rm GeV} < 300$. The most dramatic impact on the viable parameter space of the model comes from direct dark matter searches with LUX, and, for very low masses in the few GeV range, from constraints from the invisible decay width of the Higgs. In the resonant region the best constraints come from gamma-ray line searches. We show that they leave only a small region of viable parameter space, for dark matter masses within a few percent of half the mass of the Higgs. We demonstrate that direct and indirect dark matter searches (especially the search for monochromatic gamma-ray lines) will play a key role in closing the residual parameter space in the near future.